LAG()

Accesses the previous row.

Source data — Pattern 10: Window Functions

All queries run against the shared employees table (see schema.sql). This pattern introduces a sales table to demonstrate window functions including ranking, navigation, running totals, moving averages and window aggregates.

LAG() — source table 1

LAG() — source table 2

What it does

Accesses the previous row.

Problem

Display the previous month's sales.

SELECT *,
LAG(sales_amount) OVER(ORDER BY sale_month) AS result
FROM sales;

Result

LAG() — result 1